Scientific analysis of climate changes shows the world is warming up, but not in a uniform way. There are hot spots. And one of the hottest is the western Arctic, around Alaska and the northwest corner of Canada. Temperatures there have risen four to eight degrees Fahrenheit in recent decades. That’s three to five times faster than the rest of the world. The people who live in the north are now telling dramatic stories of changes they are witnessing on land and in the sea.